Two more US astro-marines died yesterday in skirmishes with Iranian cosmosoldiers on the borders of the disputed territory in outer space which the Americans controversially claimed as their own eight years ago.

The latest deaths bring to 548 the number of extraterrestrial personnel who have died during what opponents of the Cheney administration are now calling "an extra-planetary Iraq". The apparent failure of the president's pledge to "control and patrol" the galaxy threatens the Republicans' prospects in the impending midterm elections.

An official spokesman for President Cheney, who was yesterday reported to have undergone "a routine heart-transplant" at Walter Reed naval hospital in Washington, said that he was determined to keep US troops in space in order to honour a pledge made by his predecessor, President George Bush, at a similar stage in the 2006 mid-term campaign. In a policy document, the then president had declared: "Freedom of action in space is as important to the United States as air power and sea power."

Reconfirming support for these aims, President Cheney's spokesman repeated the current administration's controversial claim that the Iranian troops involved in the latest battle were "al-Qaida spacemen". The US government has consistently claimed that the Mao-Khomenei international spacestation, a joint venture between Iran and China, is in fact a training camp for terrorists intended to carry out high-altitude attacks on American cities.

Pressed on the fact that there had been no such attacks since 2001, the White House spokesman replied: "That's because our presence in the Milky Way has prevented them, you doofus." The press secretary went on to say that America's space-based army was also necessary as a first line of defence against "extraterrestrial invaders", although he accepted that none had yet been discovered.

Persistently asked whether Cheney's latest hospitalisation proved that he was wrong to have made his unexpected run for office in 2008, the aide said: "The president regularly declared in campaign speeches that he believed in American healthcare. And no previous president has ever demonstrated that faith on such a daily basis."

The White House refused to confirm or deny a report in Newsweek magazine that the fugitive terrorist Osama bin Laden has been spotted hiding on Mars and that a 10-year mission has been mounted to capture him.

Speaking at a "Down to Earth" anti-war rally in Washington, the expected Democrat candidate in the 2016 campaign, Governor Chelsea Clinton, called for American troops to be withdrawn to their "pre-2006 borders". She blamed "this discredited Buzz Lightyear foreign policy" on so-called "neo-Martians" among the White House advisers, who believe that America can only achieve national security by patrolling all the known borders of the universe. "Iraq, Iran, then the moon," Ms Clinton said. "Are we gonna have troops on Pluto next?"

As the controversy mounted, President Cheney unexpectedly issued a personal statement from the high-dependency unit, saying that Iran was part of "an intergalactic axis of evil" which "needs to be zapped". The president insisted that what he calls his "Star Wars on terror" policy must continue and signed into law an emergency bill freeing billions of dollars for developing "a big space laser-gun, sort of like they had in Flash Gordon". Just before receiving pre-operative sedation, the president pledged: "We will stay in space as long as the people of space need us."

Former President George Bush was said to be working "on a real big barbecue" at his Midland, Texas retirement ranch "and only looking at the newspapers to see if they'd make briquettes".

In London, the co-prime minister, Tony Blair, refused to put a date on when the Royal Scots Dragoon Astro-Guards might be withdrawn from their support role in the American mission. "We do not live in a country, or even in a world, we live in a universe," said Mr Blair. "And so we must stand shoulder to shoulder with America in space."

However, there are signs of tensions over this issue within Blair's New Labour party coalition with co-prime minister David Cameron's New Conservatives. Cameron said yesterday: "Moon-troops is super. But what about all those carbon emissions from the rockets?"

Political observers say that the opposition leader, Old Labour's Gordon Brown, may finally see his chance of seizing power, perhaps in a coalition with the new Liberal Democrat leader, Ms Jade Goody, the former reality TV star recently elected on a ticket to raise the struggling party's profile.

Speaking in an emergency House of Lords debate, Lord Straw of Blackburn suggested that communication problems might be arising from the thick visors which are currently standard issue for zero-gravity regiments. He called for an urgent debate on whether astro-soldiers should wear "the full helmet".